1. Field of the Invention
The invention relates to an enhanced matrix tray feeder, and in particular, to an enhanced arrangement for feeding matrix tray packaged components to a general purpose surface mount placement machine used in the manufacturing of electronic assemblies.
2. Background Information
Electronic assemblies, such as printed circuit cards, for example, are used in a variety of electrical and electronic devices to secure, arrange and interconnect a number of electrical components, for example, within the devices. Typically, the electrical components on the card include a variety of different types. For example, a card may contain electronic components contained in packaging known as chips, which are relatively small, as well as larger parts, such as plastic leaded chip carriers (PLCC) and quad flat packs (QFPs), for instance.
In general, there are two basic types of printed circuit cards. The first type includes cards having pin-through-hole parts located thereon. This type of card has a plurality of holes therethrough. The parts or components to be located on the card have legs (pins) which fit through the holes, and are crimped, for example, to secure the component to the card.
The second type of card is known as a surface mount card, which may also include pin-through-hole-parts. This type of card has a pad on a top surface thereof, on which a component lead is placed for securing the component to the card. The technology for applying the components in this manner is known as surface mount technology (SMT). The procedure associated with SMT includes, in general, the use of a screen printer, and one or more component placement machines, for example, a high-speed placer, and a general purpose placement machine. The screen printer applies solder paste to a card, whereas the component placement machines populate the card with various components, as will be described in more detail in the following paragraphs. After the card is completely populated with components, it is moved through an oven, where the solder paste is reflowed.
The screen printer is used to selectively deposit solder paste onto a bare card, i.e., a card that does not have any components thereon. A stencil is provided, which has a plurality of apertures formed therein that correspond to predetermined pad and copper plating locations to be formed on the card. The screen printer uses a set of blades to push the solder paste through the apertures of the stencil and onto the card.
After the solder paste is deposited onto the card, the card may be moved to the high-speed placer (also known as a chip shooter), and then to the general purpose placement machine. Alternatively, the card may be moved directly to the general purpose placement machine from the screen printer.
There are many types of general purpose placement machines, such as general purpose placement machine model 4861A-GSM, manufactured by Universal Instruments Corporation in Binghamton, N.Y. The general purpose placement machine is typically adapted to place a large variety of components onto the card. For example, the components can include small components, such as the aforementioned chips, as well as relatively larger components, such as quad flat packs (QFPs), ball grid array modules (BGAs), and plastic leaded chip carriers (PLCCs), for example.
The general purpose placement machine typically includes a plurality of pick-up heads, each of which is adapted to pick up a selected component for placement onto the card. For example, each head can be provided with a removable nozzle specifically adapted for the component to be picked up. When the general purpose placement machine is activated, a program is run. The program causes the heads to move and be activated in a predetermined manner, based on the type of card being built.
Typically, the components are located in one of a variety of known packaging arrangements prior to their placement onto the card. The packaging holds the components in predetermined locations, and allows for a plurality of components to be rapidly fed to the general purpose placement machine.
Moreover, the general purpose placement machine is typically adapted to hold a plurality of packaging arrangements for each type of card being built. The packaging arrangements can include, for example, a tape reel with a tape having the components located thereon. The tape is fed to the general purpose placement machine using a tape feeder, with the components being removed from the tape using the heads of the general purpose placement machine.
It is also known to package the components in tubes, with the components being sequentially arranged within the tube.
Alternatively, or in addition to the aforementioned packaging arrangements, the components can be arranged on matrix trays. Each matrix tray holds the components in a matrix formation, with the components being arranged in columns across the width of the tray, and in rows down the length of the tray. As is known, there are a large variety of matrix trays which can be used with the general purpose placement machine, depending on the size and the number of components located on the tray.
The matrix trays may be supplied to the general purpose placement machine in several different ways. For example, the general purpose placement machine may have a so-called a tray supplier device. One or more matrix trays are placed into this device, which elevates or lowers the trays to a pick-up point. The parts are then transferred from the tray to the conveyor belt, where they are subsequently picked up by the head of the general purpose placement machine.
Alternatively, the matrix trays can be individually placed on a matrix tray feeder. The matrix tray feeder, with the matrix tray located thereon, is positioned beneath the heads of the general purpose placement machine. One or more heads of the general purpose placement machine moves over a selected component in accordance with a program, and picks the component up from the matrix tray for subsequent placement onto the card.
Typically, each head uses a vacuum nozzle for picking up the components from the matrix tray feeder. The vacuum nozzles are movable in a vertical direction, i.e., toward and away from the selected components. When properly positioned, and activated by the program, the nozzle moves a predetermined distance toward the selected component, and picks the component up off from the tray using its generated vacuum. However, as will be appreciated, it is important that the component be precisely located in the vertical direction. Otherwise, when the nozzle is moved to its extreme position toward the component, the component may be too far away from the vacuum nozzle, and will not be picked up by the nozzle. Alternatively, the component may be too close to the nozzle, which can cause the nozzle or component to break when the nozzle comes in contact with the component at the nozzle's extreme position.
There are various ways in which the vertical position of the matrix tray can be set. For example, the tray can be set upon a platform specifically configured for the type of tray and/or component located thereon, so that once the tray is in place on the platform, the upper surface of the component is at the ideal height, i.e., at the height necessary for pick-up by the nozzle without damage. However, this arrangement requires a number of specifically tailored platforms, each of which is used with a specific component and/or tray. Thus, a number of different platforms must disadvantageously be manufactured and stored. Further, in order to switch from one type of tray to another type of tray, the platforms must likewise be switched. This usually requires that the operation of the general purpose placement machine be halted while the platforms are switched, resulting in a loss in production.
It is also known to provide a height adjustable platform, in which the vertical position of the platform can be adjusted. With these known platforms, the height can be adjusted using a cam lift mechanism. However, the cam lift mechanism is imprecise, and may not on its own hold the platform in the selected height during the operation of the general placement machine. As such, there is a need for a precisely adjustable platform that can retain its selected height during the entire operation of the general placement machine.
Further, the height adjustment of the known platform is accomplished while the platform is in the general purpose placement machine, making precise adjustments relatively difficult. Thus, there is a need for an adjustable platform that can be adjusted in a more user-friendly environment, such as outside of the general purpose placement machine.
Additionally, the height of the platform is usually set by "eye balling" the top of the component against some reference point while the platform is in the machine. However, this method of adjustment is imprecise. Therefore, there is a need for a precise, easy and quick way of adjusting the height of the platform.
Further, because the known platform is positioned within the machine, typically the operation of the general purpose placement machine must be halted merely to switch one empty matrix tray for a new, full matrix tray. Thus, there is a need for a platform which will allow for the loading of matrix trays without requiring that the operation of the machine be halted.